Note: If you have a line like the following in your ssh config file, then you are automatically answering “yes” to this prompt for every ssh connection.

# DON'T DO THIS! StrictHostKeyChecking false

Care about security

Since you do care about security and privacy, you want to verify that you are talking to the right server using encryption and that no man-in-the-middle can intercept your session.

There are a couple approaches you can take to check the fingerprint for a new Amazon EC2 instance. The first is to wait for the console output to be available from the instance, retrieve it, and verify that the ssh host key fingerprint in the console output is the same as the one which is being presented to you in the prompt.

Scott Moser has written a blog post describing how to verify ssh keys on EC2 instances. It’s worth reading so that you understand the principles and the official way to do this.

The rest of this article is going to present a different approach that lets you in to your new instance quickly and securely.

Passing ssh host key to new EC2 instance

Instead of letting the new EC2 instance generate its own ssh host key and waiting for it to communicate the fingerprint through the EC2 console output, we can generate the new ssh host key on our local system and pass it to the new instance.

Using this approach, we already know the public side of the ssh key so we don’t have to wait for it to become available through the console (which can take minutes).

When the instance starts running and the user-data script has executed, you can ssh in to the server without being prompted to verify the fingerprint

ssh ubuntu@$host

Don’t forget to clean up and to terminate your test instance.

rm -rf $tmpdir ec2-terminate-instances $instanceid

Caveat

There is one big drawback in the above sample implementation of this approach. We have placed secret information (the private ssh host key) into the EC2 user-data, which I generally recommend against.

Any user who can log in to the instance or who can cause the instance to request a URL and get the output, can retrieve the user-data. You might think this is unlikely to happen, but I’d rather avoid or minimize unnecessary risk.

In a production implementation of this approach, I would take steps like the following:

Upload the new ssh host key to S3 in a private object.

Generate an authenticated URL to the S3 object and have that URL expire in, say, 10 minutes.

In the user-data script, download the ssh host key with the authenticated, expiring S3 URL.

Now, there is a short window of exposure and you don’t have to worry about protecting the user-data after the URL has expired.

In a typical Amazon Web Services(AWS) Environment, Amazon Machine Images (AMIs) are strictly available in a certain region only. These AMIs cannot be moved from one region to another. Though the AMIs are shared within different Availability Zones of the same region. For this purpose, you can use a third party tool called as CloudyScripts.

CloudyScripts is a collection of tools to help you programming Infrastructure Clouds. The web-based tool is self explanatory and regularly updated. In case you find any bug, do not hesitate to email the owners right away.

AMI should be EBS-backed Linux AMI only. The AWS Access Key and Secret Key can be found at the Security Credentials page of your AWS Account. This information is unique to your account and can be misused. DO NOT share these details with anyone.

The key provided should be generated in the source and target region before using the tool. Provide the .pem key files.

AWS discourages use of “root” user for login into AWS EC2 Instances.

You may use different ssh users like, “ec2-user” for AWS Linux Instances or “ubuntu” user for Ubuntu instances.

Output will be displayed as:

Verify that the AMI is registered in the destination as Private to you i.e.owner.

If you opt to receive mail of the status, enter your email id in the status window.

Starting with the 2009-10-31 API, Amazon Web Services (AWS) has a new type of Amazon Machine Image(AMI) that stores its root device as an Amazon Elastic Block Store(EBS) volume. They refer to these AMIs as Amazon EBS-backed. When an instance of this type of AMI launches, an Amazon EBS volume is created from the associated snapshot, and that volume becomes the root device. You can create an AMI that uses an Amazon EBS volume as its root device with Windows or Linux/UNIX operating systems.These instances can be easily backed-up. You can modify the original instance to suit your particular needs and then save it as an EBS-backed AMI. Hence, if in future you need the the modified version of instance, you can simply launch multiple new instances from the backed-up AMI and are ready to-go.

Following are the steps to be performed for backup/restoring of AWS EBS instance into/from an AWS AMI. Also brief steps for deletion of AMI backup are noted for reference.

EBS-instance to EBS-backed AMI

Go to AWS Management Console and in the My Instances Pane, select the instance which has to be backed up.

Right click the instance and select option Create Image (EBS AMI).

In the Create Image dialog box, give proper AMI Name and Description. Click on Create This Image button.

The image creation will be in progress. This will take sometime depending upon the number & size of volumes attached to the instance. Click on View pending image link. It will take you to the AMIs pane.

The AMI will be in pending state. It is important to note that this AMI is private to the account and not available for AWS public use.

If you select Snapshots from the Navigation Pane, then you can see that EBS volumes attached to the instance will be backed up as too.

Once the backup is done, the AMI will be in available state.

Restore from backup AMI into instance

In case, the running instance needs to be restored, use the latest backup AMI. To launch an instance from this AMI, right-click the AMI and select Launch Instance option. The Launch Instance Wizard will be displayed, perform the usual configurations and a new instance will be created containing all the data & configurations done before backup.

Amazon Elastic Compute Cloud (Amazon EC2) is a web service that provides resizable compute capacity in the cloud. It is designed to make web-scale computing easier for developers. Amazon EC2 enables “compute” in the cloud.

Amazon Elastic Block Store (EBS) provides block level storage volumes for use with Amazon EC2 instances. EBS provides highly available, highly reliable storage volumes that can be attached to a running Amazon EC2 instance and exposed as a device within the instance. It persists independently from the life of an instance. These EBS volumes are created in a particular Availability Zone and can be from 1 GB to 1 TB in size.

Create the EBS Volume

Log into AWS Management Console and follow the below steps for all the each extra volume to be attached to instances. For example, let’s create and attach a 6GB EBS volume (for Oracle Alert Logs and Traces) to Database server.

• Choose “Volumes” on the left hand control panel:

• In the right-hand pane under EBS Volumes, click on ‘Create Volume’

• In Create Volume dialog box that appears:
Enter the size mentioned in table, keep availability zone same as that of Database instance and select No Snapshot and click on ‘Create’.

• This will create an EBS volume and once create is complete it will be displayed as

Attach Volume

• Select a volume and click on button to Attach Volume

• Select the instance for which EBS volume is to be attached. Also mention the mount point for the volume in device.
Here Instance is for database and mount device is /dev/sdf

• Once attached it will be displayed as

Mount the Volume

• Execute commands in the EC2 instance’s (Database Server) linux shell. As this is a new volume (with no data), we will have to format it
Run command:

mkfs -t ext3 /dev/sdf

(Replace text in blue with mount device used in previous step)

• Make a directory to mount the device.

mkdir /mnt/disk1

• Mount the device in newly created directory

mount /dev/sdf /mnt/disk1

(Replace text in blue as required)

• By default volumes will not be attached to the instance on reboot. To attach these volumes to given mount point every time on reboot, execute the following command

echo "/dev/sdf /mnt/disk1ext3 noatime 0 0" >> /etc/fstab"

(Replace text in blue as required)

Check attached volume by using command: df -h

Unmounting the volume

From the Elastic Block Storage Feature Guide: A volume must be unmounted inside the instance before being detached. Failure to do so will result in damage to the file system or the data it contains.

umount /mnt/disk1

Remember to cd out of the volume, otherwise you will get an error message

“umount: /mnt/disk1: device is busy”

Hope the above steps help you get into action in minutes.

In case you get stuck at any point, do comment below. I will be glad to help. 🙂

S3fs is a FUSE filesystem that allows you to mount an Amazon S3 bucket as a local filesystem. It doesn’t store anything on the Amazon EC2, but user can access the data on S3 from EC2 instance, as if a network drive attached to it.

S3fs-fuse project is written in python backed by Amazons Simple Storage service. Amazon offers an open API to build applications on top of this service, which several companies have done, using a variety of interfaces (web, rsync, fuse, etc).

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